Slot-Die Coating 30 nm Thick Perovskite Films for Large-Area Red Light-Emitting Diodes

Metal halide perovskite light-emitting diodes (LEDs) have garnered significant attention due to their superior color purity, wide color gamut, and high efficiency at high brightness. However, most high-performance perovskite LEDs are small-area devices, which are fabricated by the spin-coating method. The slot-die-coating method has shown promise in scalable fabrication in perovskite photovoltaics. However, issues related to poor wettability and slow nucleation on hydrophobic charge transport layers have hindered uniform perovskite film formation of thickness under 100 nm. To overcome this challenge, we propose an additive-engineering strategy to improve the wettability of the perovskite solution on the hydrophobic substrate by introducing polar additives into the precursor solution, which accelerates heterogeneous nucleation. Meanwhile, the decrease of colloidal size of perovskite solution effectively facilitates the solute diffusion and regulates Marangoni flow, resulting in the formation of uniform perovskite films of low roughness of 1.86 nm across 100 cm2 with a thickness of only 30 nm. Consequently, slot-die-coated red perovskite LEDs with an external quantum efficiency exceeding 21% can be achieved, and uniform electroluminescence of large-area devices (80 cm2) is demonstrated. This strategy holds great promise for the scalable fabrication of high-performance perovskite optoelectronic devices.